Infinite geometric series formula derivation ask question asked 12 years, 7 months ago modified 4 years, 9 months agoSuppose there is a family (can be infinite) of measurable spaces.What are the usual ways to define a sigma algebra on their cartesian product?There is one way in the context of defining productWhy is the infinite sphere contractible?I know a proof from hatcher p.88, but i don't understand how this is possible.
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I really understand the statement and the proof, but in my imagination thisFor many infinite-dimensional vector spaces of interest we don't care about describing a basis anyway;They often come with a topology and we can therefore get a lot out of studying dense subspaces, …Infinite decimals are introduced very loosely in secondary education and the subtleties are not always fully grasped until arriving at university.By the way, there is a group of very strict mathematicians …What do finite, infinite, countable, not countable, countably infinite mean?[duplicate] ask question asked 13 years, 2 months ago modified 13 years, 2 months ago